Power consumption is one of the factors that influences display technology. Reducing power consumption of a display makes the display more suitable for use in portable devices that use batteries to provide the power needed to operate the display. One type of display that is particularly suited for portable use is based on what is known in the art as a microdisplay. An exemplary embodiment of a microdisplay has a rectangular array of 1,024×768 pixels and the silicon die on which the pixels are located is about 13 mm×10 mm in area. The individual pixels are approximately 12 μm square.
A typical display that incorporates a microdisplay works by passing non-polarized light from an electrically-powered light source through a polarizer. The polarizer converts the non-polarized light into plane-polarized light. The polarized light illuminates the microdisplay. Each pixel of the microdisplay reflects the polarized light with the polarization of the light either rotated or not, depending on the state of an electrical signal fed to the pixel. The microdisplay reflects the light back through the polarizer, which acts as an analyzer. The analyzer causes the pixels to appear bright or dark depending on whether or not the pixel rotated the polarization of the light. The bright and dark pixels collective form a black-and-white image that can be seen by looking at the microdisplay through the analyzer using an eyepiece. Some microdisplays are capable of displaying a grey scale. Each pixel of such a microdisplay can appear bright, dark or one or more brightness levels intermediate between bright and dark. The brightness of such a pixel depends on an electrical signal fed to the pixel. Other microdisplays are capable of displaying color images.
Applications for microdisplays continue to expand. For example, displays used as the viewfinder of digital cameras and digital camcorders can be based on a microdisplay. In another example, two displays each composed of a microdisplay and associated optics are fixed to a frame, similar to an eyeglass frame, to form an eyeglass display. An eyeglass display provides the user with a private, virtual image of a virtual computer screen or video screen.
Since displays incorporating microdisplays are small enough to be portable, batteries are often used to power the microdisplay, including power for the circuits of the microdisplay and power for the light source that illuminates the microdisplay. To minimize battery weight and maximize battery life, the power consumption of the microdisplay must be minimized.
Thus, what is needed is a microdisplay having a significantly lower power consumption than a conventional microdisplay.